I teach an introductory course on mammal identification and natural history. This blog serves as a place for all of those stories, photos, facts and fun stuff that simply won't fit in the course. Type in your email below to follow this blog!

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Saturday, March 19, 2011

Friday's Black Bear Den

As I wrote in yesterday's post, I visited a bear den on Friday with some students. Our main responsibility at a visit is to gather data on the den. We describe the den itself (some are dug into the ground, others are under brush piles), measure its volume, take temperature readings inside and out of the den, record the direction of the opening, rate the level of human disturbance, etc. It took us nearly as long to take our measurements as it took the DEC to work up the adult.

Black bear den
(Dansville, NY 3/11)

This particular den was dug by the female. In this photo, look carefully to the top right of the den entrance and see an old woodchuck hole. PERHAPS the bear started her den where a similar opening already existed.

The den was on a steep slope so we didn't get too many curious visitors while we were working. Some of the measurements require a person to actually go into the den. Here, Katie's legs are visible while Bethany takes notes.

Researchers collecting bear den data
(Dansville, NY 3/11)

When it was my turn to take a look in the den, I grabbed a photo of the wall. Katie had pointed out that the individual claw marks were visible from the

excavation. Note how sandy the soil is, making the digging relatively easy. Friday was unseasonably warm. We took an outside temperature reading of 64 degrees F while it was a cooler 58F inside the den. Remember, there were four bears inside this hole. Granted, three of them are little and one of them is pretty inactive, but mom weighed 190 pounds and her three growing boys were about six pounds each. That is a lot of heat being generated! See if you can pick out any tiny scratch marks on the wall of the den from the cubs...

Wall of black bear den showing claw marks
(Dansville, NY 3/11)

My final photo of the day is perhaps my favorite. The den got measured, the sow was weighed and fitted with a new GPS telemetry collar and the cubs were weighed, measured and fitted with PIT tags (more than one person has pointed out that what we call a "den visit" is more like an "alien abduction" from the prospective of the bear). Mom was returned to her den while still under the influence of the tranquilizer and the cubs were safely tucked in behind her. As we walked away from the den, I stuck the camera in and blindly snapped a few photos. One came out very well, giving us an idea of what the first few months of life look like for a black bear.